Power operated fastener driving devices are in widespread use in the construction and building trades and typically include a power operated driving mechanism mounted within a housing that powers the driving movement of a drive element slidably mounted within a drive track that extends through a nose piece mounted to the housing. Typically when the driving mechanism is actuated, the drive element moves in a fastener driving direction through a drive stroke and then moves in the opposite direction through a return stroke during one cycle of operation. A trigger mechanism that is movable through an actuation stroke is commonly provided on the exterior of the housing to initiate an operating cycle.
A magazine assembly mounted to the housing supplies a series of fasteners to the drive track through a lateral opening in the same and the leading fastener in the drive track is driven outwardly of the drive track into a workpiece by the driving movement of the drive element when the driving mechanism is actuated. Typically a spring biased fastener feeding device advances the fasteners through the magazine toward and into the drive track.
Power operated fastener driving devices typically include a trip assembly mounted on the nosepiece and operatively associated with the trigger mechanism to prevent the driving mechanism from being actuated when the nosepiece is not in contact with a workpiece.
Often the trip assemblies of fastener driving devices include adjustable mechanisms that can be adjusted manually to control the depth to which a fastener is driven into the workpiece. A safety trip assembly including a manual adjustment mechanism is disclosed in U.S. Pat. No. 6,209,770.
Referring to FIG. 12, workpiece engaging portion 64A of the safety trip assembly 60A according to the prior art has a distal end 78A, a proximal end 88A, and a fixed locking structure 70A between the ends 78A and 88A. A movable locking member 74A releasably engages the fixed locking structure 70A to retain the workpiece engaging portion at a desired position of extension. A retaining projection 89A is integrally cast on the workpiece engaging portion 64A near the distal end 88A. The retaining projection 89A engages the movable locking member 74A at a fully extended position of the workpiece engaging portion 64A to define a maximum longitudinal length of the safety trip assembly 60A (as defined by the position of the workpiece engaging portion 64A). The safety trip assembly 60A is biased toward and into an extended position by a spring 101A. The retaining projection 89A prevents removal of the workpiece engaging portion 64A from the safety trip assembly 60A. The retaining projection 89A also prevents the workpiece engaging portion 64A from falling or dropping out of the safety trip assembly if the movable locking member 74A is depressed so that it is released from locking engagement relation with the fixed locking structure 70A and held in such relation while the fastener driving tool is in a position with the nosepiece assembly facing down. As a result, heretofore the movable workpiece engaging portion of the prior art discussed above is a permanent part of the safety trip assembly.
While the prior art described above has worked extremely well for its intended use, more recently a need has developed for a more flexible and modular tool.